The present invention relates to a controlled mounting for readily positioning and maintaining a selected desired position of a luminaire of strip type over a working or drafting surface of a drafting board hingedly mounted on a drafting table for movement between horizontal and approximately vertical positions for example from 0 to approximately 90 degrees. The strip luminaire may extend across the work surface in parallel relation to the top and bottom edges of the drafting board and may be pivotally mounted at side edges of the board for movement through a selected angle relative to the work surface on the drafting board to illuminate work areas as desired.
Many drafting boards are hingedly mounted at their bottom edge to permit positioning of the drafting board at a desired work plane. Some draftsmen prefer to draw with the drafting board horizontal or only slightly inclined. Other draftsmen prefer to draw with the drafting board inclined at a substantially greater angle such as between 45 degrees to 90 degrees. The practice of many European architect and engineering draftsmen is to position the board between 45 to almost 90 degrees. When a drafting board is in a position near horizontal and illuminated by a luminaire strip-type lighting device supported in vertical spaced relation above the drawing surface by vertically disposed support members hinged along side edges of the drafting board, it will be understood that the force moment of the weight of the strip-type luminaire device is not large, and position maintenance and stability requires minimal counterbalancing forces. Strip-type luminaire devices are usually adapted to be pivoted through an included angle of approximately 104 degrees to selectively bring effective light to a desired portion of the work surface. However when the drafting board is tilted, for example, to an angle of between 45 degrees to almost 90 degrees, the gravitational force moment acting on a strip-type luminaire device becomes substantially greater and greater counterbalancing forces are required in the mounting of the support members for the strip-type luminaire device.
Prior proposed counterbalancing means for such lighting devices for a drafting board have included friction means which may be adjustably tightened to retain the support member of a strip-type luminaire device in selected position with respect to the drafting surface for desired illumination. Such counterbalancing friction means have included adjustable friction nuts acting at the pivotal axis of the support member of the luminaire device. Piston and cylinder-type gas spring means connected between the support member of the luminaire and the drafting board have also been used. In such prior proposed counterbalancing means, the gas spring means was included on a drafting table which was specifically designed for use in a position between about 45.degree. to 90.degree.. When such specifically designed drafting table was used in a horizontal position, the gas spring means was not operable and modifications were required to be made in the support of the luminaire to facilitate its positioning during lower, near horizontal inclined positions of the drafting board.
Such prior proposed mounting means for strip-type luminaire devices included disadvantages in that positioning of the strip-type luminaire device to any position during inclination of the drafting board between 0 and 90 degrees was not accomplished without modification of the mounting means; and where gas spring means were used, the gas spring means were operable for only a portion of the inclined positions of the drafting board.